David Coley

The building performance gap: Are modellers literate?:

One of the most discussed issues in the design community is the performance gap. In this research, we investigate for the first time whether part of the gap might be caused by the modelling literacy of design teams. A total of 108 building modellers were asked to comment on the importance of obtaining and using accurate values for 21 common modelling input variables, from U-values to occupancy schedules when using dynamic simulation to estimate annual energy demand. The questioning was based on a real building for which high-resolution energy, occupancy and temperature data were recorded. A sensitivity analysis was then conducted using a model of the building (based on the measured data) by perturbing one parameter in each simulation. The effect of each perturbation on the annual energy consumption given by the model was found and a ranked list generated. The order of this list was then compared to that given by the modellers for the same changes in the parameters. A correlation analysis indicated little correlation between which variables were thought to be important by the modellers and which proved to be objectively important. k-means cluster analysis identified subgroups of modellers and showed that 25% of the people tested were making judgements that appeared worse than a person responding at random. Follow-up checks showed that higher level qualifications, or having many years of experience in modelling, did not improve the accuracy of people’s predictions. In addition, there was no correlation between modellers, with many ranking some parameters as important that others thought irrelevant. Using a three-part definition of literacy, it is concluded that this sample of modellers, and by implication the population of building modellers, cannot be considered modelling literate. This indicates a new cause of the performance gap. The results suggest a need and an opportunity for both industry and universities to increase their efforts with respect to building physics education, and if this is done, a part of the performance gap could be rapidly closed. Practical application : In any commercial simulation, the modeller will have to decide which parameters must be included and which might be ignored due to lack of time and/or data, and how much any approximations might perturb the results. In this paper, the judgment of 108 modellers was compared against each other. The results show that the internal mental models of thermal modellers disagree with one another, and disagree with the results of a validated thermal model. The lessons learnt will be of great utility to modellers, and those educating the next generation of modellers.

A Review of Current and Future Weather Data for Building Simulation

This article provides the first comprehensive assessment of methods for the creation of weather variables for use in building simulation. We undertake a critical analysis of the fundamental issues and limitations of each methodology and discusses new challenges, such as how to deal with uncertainty, the urban heat island, climate change and extreme events. Proposals for the next generation of weather files for building simulation are made based on this analysis. A seven-point list of requirements for weather files is introduced and the state-of-the-art compared to this via a mapping exercise. It is found that there are various issues with all current and suggested approaches, but the two areas most requiring attention are the production of weather files for the urban landscape and files specifically designed to test buildings against the criteria of morbidity, mortality and building services system failure. Practical application: Robust weather files are key to the design of sustainable, healthy and comfortable buildings. This article provides the first comprehensive assessment of their technical requirements to ensure buildings perform well in both current and future climates.

Overheating in vulnerable and non-vulnerable households

ABSTRACT As the 2003 European heatwave demonstrated, overheating in homes can cause wide-scale fatalities. With temperatures and heatwave frequency predicted to increase due to climate change, such events can be expected to become more common. Thus, investigating the risk of overheating in buildings is key to understanding the scale of the problem and in designing solutions. Most work on this topic has been theoretical and based on lightweight dwellings that might be expected to overheat. By contrast, this study collects temperature and air quality data over two years for vulnerable and non-vulnerable UK homes where overheating would not be expected to be common. Overheating was found to occur, particularly and disproportionately in households with vulnerable occupants. As the summers in question were not extreme and contained no prolonged heatwaves, this is a significant and worrying finding. The vulnerable homes were also found to have worse indoor air quality. This suggests that some of the problem might be solved by enhancing indoor ventilation. The collected thermal comfort survey data were also validated against the European adaptive model. Results suggest that the model underestimates discomfort in warm conditions, having implications for both vulnerable and non-vulnerable homes.

The relationship between wall reflectance and daylight factor in real rooms

To reduce lighting loads and meet targets set in building codes, architects are encouraged to make maximum use of high-reflectance colours for internal surfaces. Although in theory improving daylight factors and reducing electricity consumption of lighting circuits, this can constrain choice and may conflict with aesthetic desires. In this article, we examine the relationship between changes in surface albedo and changes in daylight factor for typical non-domestic spaces. The issue is tackled using both an analytical approach and commercial ray-tracing software such as that used by engineers for designing lighting layouts (Radiance). Unlike in design work and previous theoretical work, the fraction of surface obscured by items such as pin boards is accounted for, with the extent of such areas estimated from surveys of buildings. It is found that, within sensible bounds, changes in wall albedo have little impact on daylight factor.

SAX-quantile based multiresolution approach for finding heatwave events in summer temperature time series

Time series pattern discovery is of great importance in a large variety of environmental and engineering applications, from supporting predictive models to helping to understand hidden underlying processes. This work develops a multiresolution time series method for extracting patterns in weather records, particular temperature data. The topic is important, as, given a warming climate, morbidity and mortality are expected to rise as heatwave frequency and intensity increase. By analysing summer temperature quantiles at different levels of coarseness, it was found that compounding models can contain a complete description of severe weather events. This new multiresolution quantile approach is developed as an extension of the symbolic aggregate approximation of the temperature time series in which quantiles are computed at every stretch of the piecewise partition. The process is iterated at different scales of the partition, and it was found to be a very useful approach for finding patterns related to both heatwave periods and intensities. The method is successfully tested using real weather records from Brazil (Recife) and the UK (London), and it was found that in both locations heatwave intensity and frequency are increasing at a substantial rate. In addition, it was found that the rate of increase in intensity of the heatwaves is far outstripping the rate of increase in mean summer temperature: by a factor of 2 in Recife and a factor of 6 in London. The approach will be of use to those looking at the impact of future climates on civil engineering, water resources, energy use, agriculture and health care, or those looking for sustained extreme events in any time series.

A new way of thinking about environmental building standards: Developing and demonstrating a client-led zero-energy standard

There are over 70 low energy and carbon standards in use around the world. None of these standards have been designed by the clients who pay for and occupy the buildings in question. In this work, the client was asked to define the building code for the construction of a new 2800 m2 building via a structured survey. The resulting zero-energy standard simply required the building to incur no energy utility bill. One year of monitoring of the completed building was used to see if the standard had been met. The result of this work is a new way of thinking about environmental building standards that solves many of the issues of obtaining and maintaining buy-in from the client. Practical application: This is the first time that the client has played a key role in the definition of a low-energy building standard. Measured energy consumption and renewable energy generation data are presented and demonstrate that the zero-energy criteria were successfully met. This work is important as it shows that the client can have a meaningful input into the design of an environmental standard. The paper should be of interest to architects, engineers, building energy researchers and those interested in methods that can be used to reduce the energy demand of buildings.

RIBA President’s Awards for Research 2017 Winner of the Annual Theme - Housing: Toward healthy housing for the displaced

The population of people living in temporary settlements after disasters is in the millions and the average stay in these settlements exceeds a decade. This paper reviews the literature on the design of post-disaster relief shelters in order to: establish the state of the art, identify trends and describe the academic activity of the past forty years. The analysis demonstrates that the academic engagement in this topic is limited, with fewer than sixty publications in the past four decades. Displacement camps are often situated in countries with extreme climates; however the issue of the thermal performance of shelters and their impact on health is found to be further overlooked. In an attempt to rebalance this situation, thermal surveys were conducted in two refugee camps in Jordan. The study found that the refugees were very unsatisfied with the thermal conditions in their shelters, particularly in summer. Internal surface temperatures of 46°C were recorded in September and indoor CO2 concentration levels of 2700 ppm were measured in winter. In addition, the study reported on the adaptation strategies used by refugees to cope with the heat and cold, and on their views on shelter design considerations and satisfaction.

The reliability of inverse modelling for the wide scale characterization of the thermal properties of buildings

The reduction of energy use in buildings is a major component of greenhouse gas mitigation policy and requires knowledge of the fabric and the occupant behaviour. Hence there has been a longstanding desire to use automatic means to identify these. Smart metres and the internet-of-things have the potential to do this. This paper describes a study where the ability of inverse modelling to identify building parameters is evaluated for 6 monitored real and 1000 simulated buildings. It was found that low-order models provide good estimates of heat transfer coefficients and internal temperatures if heating, electricity use and CO2 concentration are measured during the winter period. This implies that the method could be used with a small number of cheap sensors and enable the accurate assessment of buildings’ thermal properties, and therefore the impact of any suggested retrofit. This has the potential to be transformative for the energy efficiency industry.

Data for 'Toward healthy housing for the displaced'

The population of people living in temporary settlements after disasters is in the millions and the average stay in these settlements exceeds a decade. The issue of the thermal performance of shelters and their impact on health is generally overlooked by the academic community. In an attempt to rebalance this situation, thermal surveys were conducted in two refugee camps in Jordan. Thermal monitoring data of the shelters over two weeks in summer and winter are presented in this dataset.

Refugee housing through cyclic design

ABSTRACT There are more than six million refugees living in camps globally, primarily in places with severe climates. While camps are planned to be temporary, they can be in use for decades. This ‘planned temporariness’, despite their potential longevity, together with the pressures of rapidly emerging situations, means the construction and monitoring of demonstrators is not a primary concern for their developers. This lack of iterative design improvement results in shelters with thermal environments far from ideal and a risk of increased morbidity. Here we propose a cyclical process for improving such shelters involving the thermal monitoring of pre-existing shelters to construct validated baseline simulation models of similar shelters in other areas of emerging crisis. These models can then be evolved and improved within an optimization cycle before mass-construction and field testing. Here we demonstrate the method for the case of Azraq camp in Jordan. Starting from an analysis of field survey data which exposes a high incidence of heat-stress experienced in the shelters, a series of architectural strategies are applied to the design, resulting in significant reductions in overheating. This work suggests that the proposed cyclical approach can lead to significant improvement in conditions currently experienced in refugee camp shelters.